Abstract 2994
Background
Understanding of cancer-immune system interaction led to development of immunotherapy; anti-programmed cell death protein-1 (PD-1)/programmed cell death ligand-1 (PD-L1) antibodies are now used in non small cell lung cancer (NSCLC) treatment. MAPK cascade is a key intracellular network for tumor proliferation and recent data suggest that it is implicated in interplay of tumor and T-CD8+ cytotoxic lymphocytes (CTL).
Methods
We evaluated PD-L1 mRNA level by Real Time qPCR (RT-qPCR) and its protein production, togheter with MAPK proteins, by western blot (WB), in NSCLC cell lines. Then, we studied the changes in PD-L1 and major histocompatibility complex class-I (MHC-I) expression and cytokines’ production, after MAPK-inhibition or -stimulation, by MEK-inhibitor, cobimetinib, or phorbol 12-myristate 13-acetate (PMA), respectively. In addition, we explored the effect of cobimetinib on cytokines’ genes by RT-qPCR on cDNA, obtained from retro-transcription of RNA extracted from T-lymphocytes, derived from Peripheral blood mononuclear cells (PBMC) of healthy volunteers, by density gradient separation, and activated with anti-CD3/anti-CD28 coated beads.
Results
WB and RT-qPCR for PD-L1 in NSCLC cells revealed a consistent correlation between mRNA and protein levels, togheter with activated MAPK and MEK1/2 signals, and suggested that ectopic PD-L1 mainly depends on trascriptional regulation. PDL-1 levels were significantly decreased by cobimetinib and increased by PMA, suggesting that MAPK can regulate PD-L1. Moreover, MEK-inhibition resulted on cancer cells in increased synthesis of MHC-I, IFN-gamma, IL-6, IL-1B, and TNFalpha, involved in CTL activation, and on activated human pheripheral T-lymphocytes in increment of mRNA levels of IL-12, TNFalpha and IFNgamma, that are pro-inflammatory cytokines typical of CTL subset, that seems more involved in immune response against cancer.
Conclusions
These results demonstrate that MEK-inhibion induces the establishment of a pro-inflammatory microenvironment and may represent a potential mechanism to convert otherwise resistant cancers through treatment combination strategies of MEK-inhibitors and anti-PD-L1/PD-1 antibodies in NSCLC.
Clinical trial identification
Not applicable
Legal entity responsible for the study
AOU Università della Campania “Luigi Vanvitelli”
Funding
AIRC
Disclosure
All authors have declared no conflicts of interest.